1. Technical Field
The present invention relates to a method of manufacturing a surface mounted crystal device (hereunder “surface mounted device”) and an aggregated sheet material used for this method. In particular, the invention relates to a method of manufacturing a surface mounted device in which a metal cover is jointed to each container main body by seam welding, while they are in a state of an aggregated sheet material, and an aggregated sheet material used for this method.
Since surface mounted devices, for example surface mounted resonators or oscillators are small and lightweight, they are accommodated and used especially in portable electronic equipment, as a frequency or time reference source. In recent years, due to these becoming smaller and lower cost, there is a requirement for the planar outside dimensions to be for example less than 3.2 mm×2.5 mm, and for productivity to be high.
2. Prior Art
FIG. 6 is a drawing for describing a conventional surface mounted device, for example a surface mounted resonator. FIG. 6A is its cross-section view, FIG. 6B is a plan view without a cover, and FIG. 6C is a plan view of a crystal piece accommodated inside a container main body.
In this surface mounted oscillator, a crystal piece 2 is accommodated inside a container main body 1 which has a concave cross-section, and is covered with a metal cover 3 and sealed-encapsulated. The container main body 1 comprises a laminated ceramic substrate made up of a planar first layer 1a, and a frame shape second layer 1b which has an aperture area 1c. Moreover, both sides of one edge portion of the inside bottom surface of the container main body 1 have a pair of crystal terminals 4, the four corners of the outside bottom surface have mounting terminals 5 (5a, 5b), and the aperture end face has a surface electrode 6 for sealing.
The pair of crystal terminals 4 is electrically connected for example to the mounting terminals 5 (5a, 5b) of the diagonal pair through the lamination surface of the first layer 1a and the second layer 1b. The mounting terminals 5 (5a, 5b) of the other diagonal pair are connected to a metal ring 7 comprising a thick metal film that is provided on the surface electrode 6 on the aperture end face, via an annular groove (not shown in the figure) and the lamination surfaces.
The crystal piece 2 has excitation electrodes 8 on both main surfaces, and for example, lead out electrodes 9 are extended on both sides of its one end. The both sides of one end of the crystal piece 2 are fastened to the pair of crystal terminals 4 positioned on the container main body 1, with a conductive adhesive 10, and connected electrically to one pair of mounting terminals 5 (5a, 5b). The metal cover 3 is connected by seam welding to the surface electrode 7 on the aperture end face of the container main body 1, and is electrically connected to the other pair of mounting terminals 5 (5a, 5b) serving as ground terminals.
In order to manufacture these kinds of surface mounted devices, as shown in FIG. 7, for example, in a state of an aggregated sheet material 12 with several container main bodies 1 partitioned by lengthwise and crosswise V-grooves (parting grooves) 11, at first the aggregated sheet material 12 is parted into individual container main bodies 1 along the lengthwise and crosswise V-grooves 11. Next a crystal piece 2 is accommodated inside each container main body 1. Finally the metal covers 3 are respectively bonded to the individual container main bodies 1.
Here, the aggregated sheet material 12 comprises a planar first layer 12a made of a ceramic sheet, and a second layer 12b that has a plurality of apertures 12c. Furthermore, for each of the container main bodies 1 comprising the first layer 12a and the second layer 12b, there is printed for each of the layers, an underlay pattern of an electrode pattern that includes the aforementioned (FIG. 6) crystal terminals 4, mounting terminals 5, annular grooves, and surface electrodes 6. The underlay pattern (underlay electrode) is composed of for example, tungsten (W) or molybdenum (Mo).
Then, after laminating the first layer 12a and the second layer 12b, and integrally baking, the underlay electrodes of the crystal terminals 4, the mounting terminals 5, and the surface electrode 6 that are exposed on the external surface of the aggregated sheet material 12, are formed by electro plating or electroless plating nickel (Ni) or chrome (Cr), and then gold (Au).
For example, in the case of electro plating, the underlay electrodes of the respective container main bodies 1 are commonly connected electrically through an underlay circuit 13 (refer FIG. 7) provided on the lamination surface. Then, after connecting the underlay circuit 13 to the cathode (−), the aggregated sheet material 12 is immersed in an electrolyte, and nickel (Ni) (or chrome (Cr)) and then gold (Au) are deposited by electro plating onto the exposed underlay electrodes of the respective container main bodies 1.
When seam welding the metal cover onto the container main body 1, as shown in FIG. 8A and FIG. 8B, for example, the individual container main bodies 1 that have a crystal piece 2, are accommodated in an aperture part 14a of a carrier plate 14. Then the carrier plate 14 is moved in a direction for seam welding, and the container main body 1 and the metal cover 3 are image recognized, the metal cover 3 is positioned on the container main body 1, and is tacked at two places for example.
Then after tacking, the carrier plate 14 is further moved, a movable rod 15 is raised, and the container main body 1 is pushed up, so that the opposite sides of the metal cover 3 are abutted against a pair of electrode rollers 15a and 15b. Then between the pair of electrode rollers 15a and 15b is electrified, and while moving the container main body 1 and the metal cover 3, the abutted pair of opposite sides are welded by Joule heat. Next the movable rod 15 is rotate through 90 degree, and the electrode rollers 15a and 15b are abutted against the other pair of opposite facing sides, and similarly welded.